We shall study the expression of proinsulin in bacteria. We will construct a number of different fusion proteins which fuse different portions of the penicillinase gene and its hydrophobic signal sequence to the structural sequence of the rat preproinsulin gene in order to study the secretion and processing of these fused proteins. We will study the chromosomal insulin genes of the rat and other species in order to infer the ancestral gene structure and to discover whether introns, interruptions in coding sequences, are inserted or deleted over evolutionary times.